After less than a year on the job, all 20 members of the police force in the northern Mexican town of Ascension resigned on Thursday.

The move came in response to months of violent exchanges with drug traffickers.

In mid-May, police chief Manuel Martinez and two officers were kidnapped. The following day, their bullet-ridden bodies were discovered in the back of a car on a nearby highway. On Tuesday, gunmen shot and killed three more police officers, Chihuahua state chief prosecutor Carlos Manuel Salas said.

The entire force was installed last September after angry residents claimed the former police officers were helping local drug gangs commit crimes. The new officers tried to quell the violence by installing a security camera and digging a ditch around the town, but the attacks continued.

State and federal police will patrol Ascension until replacements can be hired.